1. Field of the Invention
This invention is in the field of tools used downhole in oil or gas wells to perform functions such as orienting a tool, drilling a borehole, or milling or cutting a casing positioned in a borehole, using a non-rotating work string. Specifically, this invention concerns a tool used to prevent the imposition of reactive torque on a non-rotating work string when a downhole motor is used, or when a downhole tool is turned for some other purpose.
Background Information
This application will refer to operations being conducted in a borehole, with the understanding that there may or may not be a casing in place in the borehole, and references to a borehole or borehole wall are intended, where appropriate, to include reference to a casing or casing wall, within a borehole, as will be apparent from the context. Downhole operations in an oil or gas well are often conducted by tools attached to the lower end of a length of small diameter, or relatively thin, non-rotating tubing which has been positioned in the borehole. Many such downhole operations, for example, will be conducted with "coiled tubing" which has been uncoiled and run into the borehole.
Such operations often require the rotation of a tool at the downhole end of the stationary work string tubing. Rotation of the downhole tool may be a continuous forceful rotation, accomplished by means of a downhole motor, such as a mud motor, as is often done to rotate a drill bit, a milling tool, or a casing cutter. Further, a downhole tool may be rotated incrementally, and less forcefully, to orient a tool face in a desired direction. In the case of continuous forceful rotation, the downhole motor also imparts a forceful reactive torque to the work string to which it is attached, which can even exceed the torque limit of the work string. In the case of less forceful incremental rotation, reactive twisting of the work string, however slight, can cause inaccuracy in the orientation of the downhole tool. In either case, it would be desirable to have a torque barrier which can be installed between the non-rotating work string and the downhole rotating tool, to prevent the imposition of reactive torque on the work string uphole from the torque barrier.